In one aspect of the related art, a wireless communication system comprises a set of devices supporting at least one of a single-carrier (SC) physical (PHY) layer and an Orthogonal Frequency Division Multiplexing (OFDM) physical layer may be used for millimeter wave communications, such as the systems envisioned in the Institute of Electrical and Electronic Engineers (IEEE) 802.11.ad and IEEE 801.15.3c standards, and the Wireless Gigabit Alliance (WGA). The PHY layer may be configured for millimeter wave communications in the spectrum of 57 to 66 gigahertz (GHz), or Ultra Wide Band (UWB) communications in the spectrum of 3.1 to 10.6 GHz.
To allow interoperability between devices or networks that support either single-carrier or OFDM PHY modes, all devices further support a common mode referred to as a control PHY. Specifically, the common mode is a single-carrier base-rate mode employed by both OFDM and single-carrier devices to facilitate co-existence and interoperability between different devices and different networks. The common mode may be employed for beaconing, control, management, and communicating command and data frames (packets).
In another aspect of the related art, devices typically employ one or more Golay codes to provide spreading of different fields of a packet. Complementary codes, first introduced by Golay in M. Golay, “Complementary Series,” IRE Transaction on Information Theory, Vol. 7, Issue 2, April 1961, are sets of complementary pairs of equally long, finite sequences of two kinds of elements. These complementary pairs have the property that the number of pairs of like elements with any given separation in one code is equal to the number of unlike elements with the same separation in the other code. The complementary codes first described by Golay were pairs of binary complementary codes with elements +1 and −1, wherein the sum of their respective aperiodic autocorrelation sequence is zero everywhere, except for the center tap.
In a wireless network, such as a wireless personal area network (WPAN) or a wireless local area network (WLAN), devices typically use a slotted ALOHA protocol or a carrier sense multiple access/collision avoidance (CSMA/CA) protocol to access the wireless medium. However, these access methods do not perform well when one or more devices use directional antenna patterns for their transmissions and/or receptions.
Therefore, there is a need in the art for a directional channel access protocol for devices that may have directional antenna systems, such as phased antenna arrays, directional antennas, or sectored antennas.